JP2006249576A - Gas supply tube for plasma treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas supply tube for plasma treatment, wherein clogging is hardly caused by the sticking of vapor deposition components, and further, the peeling of the stuck vapor deposition components is effectively suppressed, and uniform gas supply can be performed stably over a long period. <P>SOLUTION: In the gas supply tube which is inserted to the inside of a vessel held inside a plasma treatment chamber, for supplying gas for plasma treatment into the vessel, a gas flow passage is extended in the axial direction, also at least the surface part in the tube wall is formed of a porous body, and, gas blowout holes with a diameter of ≥0.2 mm are formed at suitable intervals in the axial direction or circumferential direction in the tube wall. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma processing gas supply pipe used when forming a deposited film on the inner surface of a container such as a plastic bottle by a plasma CVD method.

  Chemical vapor deposition (CVD) is a technology that deposits reaction products in the form of a film on the surface of a substrate by vapor phase growth in a high-temperature atmosphere using a source gas that does not react at room temperature. The technology is widely used for surface modification of ceramics and ceramics, and is recently being used for surface modification of containers such as plastic bottles, particularly for improving gas barrier properties.

  Plasma CVD is a method of growing a thin film using plasma. Basically, a gas containing a raw material gas is discharged under a reduced pressure with electric energy by a high electric field, decomposed, and a generated substance is gasified. It consists of a process of depositing on a substrate via a chemical reaction in phase or on the substrate. The plasma state is realized by glow discharge, and a plasma CVD method using microwave glow discharge, a plasma CVD method using high-frequency glow discharge, and the like are known depending on the glow discharge method.

  In both the microwave and high frequency plasma CVD methods, in order to form a deposited film on the inner surface of the container, the container is held in the plasma processing chamber and a reactive gas (plasma processing gas) is supplied into the container. The inner surface of the container is generated by generating a glow discharge by microwave or high frequency in the container while supplying a reactive gas to the inside of the container while reducing the pressure in the container to a predetermined degree of vacuum. A vapor deposition film is formed on the substrate.

Therefore, in order to form a vapor deposition film having a uniform thickness on the inner surface of the container, it is necessary to uniformly supply a reactive gas into the container. As such a gas supply pipe, a porous body pore is provided. A porous pipe serving as a gas blowing hole or a perforated pipe in which a gas blowing hole is formed by drilling or the like on a wall surface of a metal pipe or the like has been proposed (see Patent Document 1).
JP 2003-54532 A

  However, when forming a vapor deposition film by a plasma CVD method on the inner surface of the container using a gas supply pipe made of a porous pipe as shown in Patent Document 1, the gas is repeatedly formed while the vapor deposition film is repeatedly formed. There has been a problem that vapor deposition film components adhere to the outer peripheral surface of the supply pipe and the gas holes of the supply pipe are clogged. When such clogging occurs, for example, the reaction gas is almost blown out from the tip of the gas supply pipe, and as a result, the vapor deposition film is formed on the bottom of the container facing the tip of the gas supply pipe. As a result, the thickness of the deposited film such as the inner surface of the body of the container becomes extremely thin. Moreover, in the perforated pipe as described in Patent Document 1, since the gas blowout holes are relatively large, clogging hardly occurs even if the vapor deposition component adheres to the tube wall, but adheres to the tube wall. Vapor deposition components peel off from the tube wall during the vapor deposition process and adhere as foreign matter to the inner surface of the container on which the vapor deposition film is to be formed, resulting in variations in the thickness and composition of the vapor deposition film and obtaining desired characteristics. There was a problem that it was not possible. Therefore, in order to cause such a problem, the conventionally known gas supply pipe must be frequently replaced, and the improvement is demanded at present.

  Therefore, an object of the present invention is to provide a plasma processing apparatus that is less likely to be clogged due to adhesion of vapor deposition components, and that effectively prevents peeling of the deposited vapor deposition components and can stably supply a uniform gas over a long period of time. It is to provide a gas supply pipe.

According to the present invention, in the gas supply pipe inserted into the container held in the plasma processing chamber and supplying the plasma processing gas into the container,
The gas flow path extends in the axial direction, and at least the surface portion of the tube wall is formed with a rough surface. The tube wall has a diameter of 0.2 mm at an appropriate interval in the axial direction or the circumferential direction. A gas supply pipe for plasma processing is provided in which the above gas blowing holes are formed.

In the gas supply pipe for plasma processing in the present invention,
1. The tube wall is formed of a porous body;
2. The tube wall is formed of a sintered body;
3. The surface of the tube wall is formed by alumite treatment;
Is preferred.

  In the present invention, at least the surface of the tube wall is formed with a rough surface, and the gas blowing hole has a diameter of 0.2 mm or more (that is, not a pore of a porous body, such as a perforation). An important feature is that the blowout holes are formed by large holes formed by post-processing. That is, since the gas blowing holes have a large diameter, clogging of the gas blowing holes can be effectively prevented even when a vapor deposition component adheres to the tube wall surface. For example, when the gas blowing holes are formed by the pores of the porous body, clogging easily occurs due to adhesion of the vapor deposition components, so that the supply of the reactive gas becomes uneven and the thickness of the vapor deposition film becomes uneven. Etc. will occur. In addition, even if deposition components adhere to the tube wall surface, because the surface is formed of an uneven rough surface or a porous body, the deposited components are firmly held on the tube wall surface, As a result, it is possible to effectively avoid the adhesion of foreign matters to the inner surface of the container due to the removal of the vapor deposition components, and a vapor deposition film having a uniform thickness and composition can be formed. For example, in a tube formed of a metal material having a smooth surface, the deposited components easily fall off, and foreign matter adheres to the inner surface of the container.

  As described above, according to the present invention, even when the plasma treatment is repeatedly performed over a long period of time, it is possible to stably and uniformly supply a gas without causing foreign matter to adhere to the inner surface of the container.

Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.
FIG. 1 is a conceptual diagram showing a process for forming a vapor deposition film on the inner surface of a container by plasma processing performed using the gas supply pipe of the present invention, and is a diagram illustrating microwave CVD as an example.
FIG. 2 is a cross-sectional side view showing a preferred example of the gas supply pipe of the present invention.

  That is, the process of forming a deposited film on the inner surface of the container by plasma processing will be described taking microwave CVD as an example. As shown in FIG. 1, the plasma processing chamber 1 has a microwave supply member such as a waveguide. 3 is connected. The plasma processing chamber 1 is formed of a metal chamber for confining electromagnetic waves (microwaves). A container (for example, plastic bottle) 5 to be processed is held in an inverted state in the plasma processing chamber 1, and the gas supply pipe 10 of the present invention is inserted into the container 5. The gas supply pipe 10 is disposed so that the base portion thereof is located in the neck portion of the container 5 so that the reactive gas is supplied to the entire container 5 as evenly as possible.

  In FIG. 1, the exhaust or supply mechanism or the like in the plasma processing chamber 1 is omitted, and the gas supply pipe 10 is schematically shown, and its detailed structure is shown in FIG.

  During plasma processing, the inside of the container 5 is maintained in a vacuum state by a predetermined exhaust mechanism, and at the same time, the inside of the plasma processing chamber 1 (outside the container 5) is also in a reduced pressure state in order to prevent deformation of the container 5 due to external pressure. To do. In this case, the degree of decompression is high in the container 5 so that microwaves are introduced and glow discharge is generated, while the plasma processing chamber 1 is such that glow discharges are not generated even when microwaves are introduced. The degree of decompression is low.

  After maintaining the inside and outside of the container 5 in a predetermined reduced pressure state as described above, a reactive gas is introduced into the container 5 through the gas supply pipe 10, and microwaves are introduced into the plasma processing chamber 1 through the microwave transmission member 3. Introduce and generate plasma by glow discharge. The electron temperature in this plasma is tens of thousands of K, the temperature of gas particles is about two orders of magnitude higher than that of several hundred K, and is in a thermally non-equilibrium state, compared to a low-temperature plastic substrate. However, plasma treatment can be performed effectively.

  The reactive gas is reacted by the plasma, and a vapor deposition film is deposited on the inner surface of the container 5. After performing such plasma treatment to form a vapor deposition film having a predetermined thickness on the inner surface of the vessel 5, the introduction of the reactive gas and the introduction of the microwave are stopped, and the inside of the plasma treatment chamber 1 and the vessel 5 is cooled. Air is gradually introduced to return the inside and outside of the container 5 to normal pressure, and the plasma-treated container 5 is taken out of the plasma processing chamber 1.

  In the above plasma treatment, the container 5 may be made of any plastic, and the shape of the container 5 is not limited, and may be any shape such as a bottle, a cup, and a tube.

  As the reactive gas, an appropriate gas is used according to the type of vapor deposition film formed on the inner surface of the container 5. For example, it is preferable to use a compound containing atoms, molecules or ions constituting the thin film in a gas phase and placed on a suitable carrier gas. Hydrocarbons such as methane, ethane, ethylene, and acetylene are used for forming the carbon film and the carbide film. For forming the silicon film, silicon tetrachloride, silane, an organic silane compound, an organic siloxane compound, or the like is used. Halides (chlorides) such as titanium, zirconium, tin, aluminum, yttrium, molybdenum, tungsten, gallium, tantalum, niobium, iron, nickel, chromium, and boron, and organometallic compounds can also be used. Further, oxygen gas is used for forming the oxide film, and nitrogen gas or ammonia gas is used for forming the nitride film. These source gases can be used in appropriate combination of two or more kinds depending on the chemical composition of the thin film to be formed. As the carrier gas, argon, neon, helium, xenon, hydrogen and the like are suitable.

  The gas supply pipe 10 of the present invention used for the above-described plasma processing has a structure as shown in FIG. That is, a gas flow path 10a extending in the axial direction from the root portion toward the tip end portion is formed inside the gas supply pipe 10, and the base portion of the gas flow path 10a is opened to a predetermined level. A predetermined reactive gas is connected to the air supply system and introduced into the gas flow path 10a.

  Further, gas blowing holes 12 are formed on the wall surface of the gas supply pipe 10 at appropriate intervals in the axial direction and further at appropriate intervals in the circumferential direction by processing means such as laser processing and punching. Over almost uniformly distributed.

  Further, the gas flow path 10a may extend to the distal end portion with a constant diameter and penetrate the distal end wall, but generally penetrates the distal end wall as shown in FIG. The portion (shown by 10b) is preferably narrowed to the same diameter as the gas blowing hole 12. If the tip wall is closed, the gas supply to the bottom of the container 5 is insufficient, and if the diameter of the tip wall portion 10b of the gas flow path 10a is larger than the gas blowing hole 12, the tip wall portion 10b This is because the amount of gas blowout may be larger than other portions.

  In the present invention, it is important that the diameter of the gas blowing hole 12 is 0.2 mm or more. That is, by setting the diameter of the gas blowing hole 12 large, clogging of the gas blowing hole 12 due to adhesion of the vapor deposition component can be effectively avoided. On the other hand, if the diameter is increased more than necessary, the amount of gas blown out tends to be non-uniform. For this reason, the diameter is preferably 3 mm or less.

  In the present invention, at least the surface of the tube wall of the gas supply tube 10 must be formed with a rough surface. That is, by forming the tube wall surface with a rough rough surface, even if vapor deposition components adhere to the tube wall surface by performing the plasma treatment described above, the deposited vapor deposition components are firmly held on the tube wall surface. Therefore, the dropout is effectively suppressed, and the adhesion of foreign matter to the inner surface of the container due to the dropout of the vapor deposition component can be effectively avoided.

Therefore, in general, the gas supply pipe 10 of the present invention is preferably formed of a porous body or a sintered body in order to make the surface rough. For example, the gas supply pipe 10 can be formed by sintering using various ceramic powders typified by alumina, bronze powder particles, stainless steel powder particles, or the like. In general, it is preferable to have an opening (that is, the degree of pore size) such that the nominal filtration accuracy is 300 μm or less, particularly 1 to 150 μm. The nominal filtration accuracy is one of characteristic values used when a porous material is used as a filter. For example, the nominal filtration accuracy of 130 μm is the above-mentioned particle size when this porous material is used for a filter. This means that a foreign substance having a diameter can be captured.
In addition, since the surface only needs to be formed of a porous body, for example, by performing alumite treatment on the surface of an aluminum tube formed by metal processing, a gas is formed by forming a porous layer made of an alumite layer. The supply pipe 10 can also be formed.

  In addition, since the pore in the porous body forming the tube wall surface does not function as a gas blowing hole, the porous body may be densely formed so that gas blowing from the pore does not occur. .

  In the present invention, the gas supply pipe 10 described above may have a length that extends from the neck of the container 5 to the vicinity of the bottom, but the gas supply pipe 10 is formed of a metal material. If it is, the length L is preferably determined by a function of a half wavelength of the microwave determined by the size of the plasma processing chamber 1 and the position of the microwave transmission member 3. That is, by setting the length of the metal supply pipe 10 in this way and inserting it into the container 5 to perform the plasma treatment, the electric field strength distribution along the axial direction of the container 5 is stabilized, and the vapor deposition film This is because uneven thickness can be prevented.

  In the above-described example, the plasma processing by microwave glow discharge has been described as an example. However, the gas supply pipe 10 of the present invention as described above can also be applied to plasma processing by high-frequency glow discharge. In the plasma treatment by high frequency, a high frequency external electrode is provided in the vicinity of the outer surface of the container, a ground electrode is provided inside the container, and plasma treatment is performed by generating a high frequency, and a minute condition such as a degree of vacuum in the container. The plasma treatment is basically performed in the same manner as in the case of microwaves. Therefore, by using the gas supply pipe 10 of the present invention, it is possible to effectively suppress clogging due to adhesion of vapor deposition components and adhesion of foreign matters to the inner surface of the container 5 due to falling off of the deposited vapor deposition components.

  According to the gas supply pipe 10 of the present invention having the above-described structure, clogging of the gas supply hole due to adhesion of vapor deposition components and foreign matter adhesion to the inner surface of the container can be effectively avoided, so that plasma treatment is stably and repeatedly performed over a long period of time. be able to.

The following examples illustrate the superior effects of the present invention.
[Common conditions]
A PET bottle having a mouth nominal diameter of φ28 mm was used as the substrate to be plasma treated. As the processing gas, an organosilicon compound gas and an oxygen gas were used, and the gas flow rates were 2 sccm and 20 sccm, respectively. The degree of vacuum inside and outside the bottle during the plasma treatment was adjusted to 20 Pa and 7000 Pa, respectively, so that the plasma was excited only inside the bottle when microwaves were supplied. The microwave was oscillated using a commercially available microwave power source (2.45 GHz) and supplied into the plasma processing chamber with an output of 500 W. The plasma treatment time was 10 seconds after plasma ignition.
[Evaluation]
The above-described series of treatments were continuously operated for 24 hours, and the state of deposition of the deposited film components on the gas supply pipe was confirmed.

[Experimental example]
Experiments were performed with a combination of supply pipe specifications and drill hole conditions as shown in Table 1. Here, a cylindrical tube with a nominal filtration accuracy of 10 μm was used as the SUS sintered body. The spiral machining in Comparative Example 4 is one in which a single thread having a pitch of 0.75 mm is machined on the surface of the supply pipe.

[Examples 1 to 3]
From Table 1, under the experimental conditions (Examples 1 to 3) satisfying the claims of the present invention, after 4 days of continuous use, the gas supply pipe is not clogged or the residue attached during vapor deposition does not occur, which is very good. there were.

[Comparative Examples 1-4]
When there is no drill hole as in Comparative Example 1 or when the drill hole diameter is as small as less than 0.2 mm as in Comparative Example 2, deposition of vapor deposition components on the surface of the gas supply pipe becomes clogged. As a result, the continuous use days decreased. In addition, when the surface of the gas supply pipe was not treated as in Comparative Example 3, dropping of the residue adhering during vapor deposition occurred in a short time. When the surface of the gas supply pipe was processed into a spiral shape as in Comparative Example 4, the trapping effect of the vapor deposition component was not observed, and eventually the residue attached during vapor deposition occurred.

It is the conceptual diagram which shows the formation process of the vapor deposition film of the container inner surface by the plasma processing implemented using the gas supply pipe | tube of this invention, and is the figure shown taking microwave CVD as an example. It is a sectional side view showing a suitable example of a gas supply pipe of the present invention.

Explanation of symbols

10: Gas supply pipe 12: Gas blowout hole

Claims (4)

In a gas supply pipe for supplying a plasma processing gas into the container inserted into a container held in the plasma processing chamber,
The gas flow path extends in the axial direction, and at least the surface portion of the tube wall is formed with a rough surface. The tube wall has a diameter of 0.2 mm at an appropriate interval in the axial direction or the circumferential direction. A gas supply pipe for plasma processing, wherein the gas blowing holes are formed.   The plasma processing gas supply pipe according to claim 1, wherein the pipe wall is formed of a porous body.   The plasma processing gas supply pipe according to claim 1, wherein the pipe wall is formed of a sintered body.   The plasma processing gas supply pipe according to claim 1, wherein a surface of the pipe wall is formed by alumite treatment.

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